Color diffusion transfer process photographic light-sensitive materials have been put into practice as "instant" photographic materials. Such materials make it possible to enjoy color photographic picture immediately after photographing. These types of light-sensitive materials are designed so that they are extruded out of a camera (or dark box) immediately after taking a picture. This permits a photographer to consecutively release the shutter. With light-sensitive materials of this type, a light-sensitive layer is designed to be sandwiched, after photographing, between two light-sealed (or sealing) layers usually containing carbon black so as to protect it from the following deleterious exposure. Carbon blacks employed in the prior art light-sealing layers are not subjected to "forced oxidation" (later defined) though some carbon blacks inherently undergo oxidation during their production; however, such oxidation inherent to a manufacturing process is fundamentally different from "forced oxidation" as is called for in the present invention. To distinguish such inherent oxidation from and as opposed to "forced oxidation," the term "nontreated" is often used hereafter to refer to carbon blacks commercially available, some of which are inherently oxidized during a manufacturing process. Light-sensitive materials designed as described above have long been proposed and described, for example, in U.S. Pat. No. 3,053,659.
However, formation of the light-sealed (or sealing) layers using non-treated carbon black has involved the defect that, upon production and during storage of the light-sensitive materials, the light-sealed (or sealing) layers adversely influence a silver halide emulsion layer in the vicinity thereof by increasing the minimum desity (Dmin) or decreasing the maximum density (Dmax) of the resulting transfer image. This defect is particularly serious when "direct positive emulsion of the type not previously fogged" is used as a silver halide emulsion. Also, formation of the light-sealed (or sealing) layers using non-treated carbon black has involved the defect that, upon diffusing of transferred dyes through the layers, the dyes are captured by (or adsorbed on) carbon black. This results in a decrease in the maximum density of the transferred dye image or delayed appearance of the image.
U.S. Pat. No. 3,900,323 proposes to add water-soluble salts of heavy metals such as cadmium or lead to the carbon black-containing layer for preventing formation of fog due to the use of carbon black. However, the use of such heavy metal salt can cause environmental pollution and, in addition, involves the technical problem that it is difficult to control the amount of heavy metal salt to the lot-to-lot change in the amount of impurities (sulfur compounds) in carbon black. Further, when the heavy metal salt is used in excess amount, the heavy metal salt itself adversely influences photographic properties decreasing photographic sensitivity (leading to fluctuation in photographic quality due to lot-to-lot variation of carbon black).
Carbon black being available on a market has a particle size of 0.018 to 0.12.mu.. Among above-mentioned carbon blacks, the carbon black having a particle size of 0.018 to 0.030.mu. is unsuitable for incorporated into a light-sealed (or sealing) layer, because the surface area of said carbon black being large, the dye adsorption of said carbon black is much.
Research Disclosure, No. 15162, page 83, November (1976) discloses diffusion transfer films containing carbon black, particularly noting that it is preferred that carbon black particles have non-oxidizing surfaces. This is assumed to be because that oxidized surfaces would adversely affect an oxidation reduction mechanism in photographic systems. Further, it is known by Myers et al, Pigments, vol. 3, page 275, published by Marcel Dekker (1975) that oxidation produces an increase in surface area and, based on this established knowledge, it is highly likely that the Research Disclosure article teaches to avoid the use of carbon black particles having an oxidized surface. According to the Meyers et al article, air oxidation of carbon black particles produces as much as a 6 to 8 times increase in surface area. Carbon black particles having such a large surface area are not effective for the use of the present invention.
In addition, the use of carbon black is disclosed in U.S. Pat. Nos. 4,272,594 issued to George et al, 3,267,871 issued to Abott, 3,900,323 issued to MacLeish et al and 4.076,531 issued to Crowell; however, carbon black used therein are all non-treated carbon atoms and involve disadvantages as will later be demonstrated in comparative examples.